Android 8.1.0 (Oreo) is an older operating system, but it is still supported by the Google Play Store
The Google Play Store APK is the installer package for the official Android app marketplace. Installing it manually can help when:
By updating your APK to the latest version compatible with Android 8.1.0, you get the latest definitions. This service scans your apps daily to ensure no malware or "Potentially Harmful Applications" (PHAs) are present on your phone. Conclusion